Thread: 3.9 v8 temperature sender

Originally Posted by bee utey

The black one way valve connects to the evap canister. It is the one broken off the filler assembly. The white one is a relief valve to atmosphere. The separation chamber on the filler pipe is exactly the same height as before, the tank itself is supposed to be filled to the level of the pump flange as the fill pipe should extend to that depth.

Below is what a well designed corner tank looks like with an unmolested filler pipe assembly. Ignore the modded part towards the camera, it is for converting this tank for additional diesel capacity next to a steel long range tank. They will be joined under the chassis by hose.

Pefect, thanks a picture is always worth a 1000 words. I can now tell it was the LPG fitter that modified all of this.

Out of interest you will fill the secondary tank with your modification, but how will you pickup fuel from it. I'm guessing you run multiple tank pumps with one way valves in there output lines?

seeya,
Shane L.

Thinking about this. Why don't we just ignore the separation tank (what a crazy idea). If I could get a simple 'T' piece I'd run the tank vent line up high into the wheel arch (higher than the filler tube so in theory it would never fill with petrol) .... Then hook it straight to the charcoal canister ... Using a "T" piece so I can also plumb in the over-pressure valve.

I don't understand why they used that separator rather than just running the breather line higher than the filler

seeya,
Shane L.

Originally Posted by DoubleChevron

Out of interest you will fill the secondary tank with your modification, but how will you pickup fuel from it. I'm guessing you run multiple tank pumps with one way valves in there output lines?

Nothing of the sort.

Originally Posted by bee utey

They will be joined under the chassis by hose.

The lowest point of the sub tank (the drain plug) will be joined under the chassis rail to the lowest point of the main tank and the fuel will be drawn from that tank as per usual. The EFI pump assembly in the sub tank will be reduced to the function of a hole plug.

Originally Posted by DoubleChevron

Thinking about this. Why don't we just ignore the separation tank (what a crazy idea). If I could get a simple 'T' piece I'd run the tank vent line up high into the wheel arch (higher than the filler tube so in theory it would never fill with petrol) .... Then hook it straight to the charcoal canister ... Using a "T" piece so I can also plumb in the over-pressure valve.

I don't understand why they used that separator rather than just running the breather line higher than the filler

seeya,
Shane L.

Land Rover designed the filler pipe assembly, it does work quite well and should work just as well with your sub tank so long as you don't over fill it or have massive holes into the passenger space. Raising the breather does nothing if your filler cap is in good condition as no fuel can escape there.

Originally Posted by bee utey

Nothing of the sort.




The lowest point of the sub tank (the drain plug) will be joined under the chassis rail to the lowest point of the main tank and the fuel will be drawn from that tank as per usual. The EFI pump assembly in the sub tank will be reduced to the function of a hole plug.




Land Rover designed the filler pipe assembly, it does work quite well and should work just as well with your sub tank so long as you don't over fill it or have massive holes into the passenger space. Raising the breather does nothing if your filler cap is in good condition as no fuel can escape there.

Oh, I'm not good at reading stuff am I

With the separation tank breather, it has nothing to do with the filler assembly. It's hooked to the vent on the top of the tank .... The other side of the separation tank runs forward to the charcaol canister. it's just built into the filler tube as I guess that was the easiest place to attach it.

Oh bugger, running the line up high will not help. As the tank can be slightly pressurised, we can readily push raw petrol up into that separator due to pressure build up in the tank if the tank is full. (ie: filled to the top of the filler tube so the bowser has cut out). Now I think about it. If you fill the tank to the top, buy design it's going to push raw fuel forward to the charcoal canister.

If you fill it on a cold morning, then park the car in the sun on a hot day, the fuel will expand and pressurise the main tank... which will push the fuel up the breather line into the separation tank. If the pressure is great (ie: very cold when filled, very hot at the end of the day) that tiny separator tank will fill with petrol and possibly overflow, then the petrol will be drawn into the charcoal as soon as the charcoal canisters vent solenoid opens to allow the engine to burn the fumes.

This is a really silly design. I'm sure it works somewhere where it doesn't get really hot so the petrol expands a lot.

seeya.
Shane L.

The expansion tank is supposed to act as a buffer to absorb the amount of fuel that will be pushed out from petrol expansion, and then flow back into the tank as fuel is used or cooled to stop raw fuel getting into the charcoal canister., and you sure do not want that.
There is a different design of steel expansion tank on earlier models which looks to have a bigger volume and AFAIR sits higher in the guard.

Just pay attention to this as it was a real PITA when I had an inside LR tank although I never had fumes as all vents were sealed in the inner guard.

Anyway it looks like you are well on the way to solving the problem.

Regards Philip A

One final reply before I give up in frustration. The expansion space you need for normal duty is the part of the petrol tank above the line of the fuel pump assembly's mounting face. If properly designed, a fuel tank causes the servo's delivery nozzle to click off at this level, usually by having the fill pipes dip into the tank at that level. It's when fools think that they can trickle fill a tank to the very brim that problems appear in this scenario. The separator's job is to ensure that fuel splash doesn't make it into the charcoal canister line, it does not take the place of the tank's own expansion space.

Shane - this might work - ordered but not used as yet, so can't comment.

Originally Posted by bee utey

One final reply before I give up in frustration. The expansion space you need for normal duty is the part of the petrol tank above the line of the fuel pump assembly's mounting face. If properly designed, a fuel tank causes the servo's delivery nozzle to click off at this level, usually by having the fill pipes dip into the tank at that level. It's when fools think that they can trickle fill a tank to the very brim that problems appear in this scenario. The separator's job is to ensure that fuel splash doesn't make it into the charcoal canister line, it does not take the place of the tank's own expansion space.

I feel your frustration



THis will work as you describe. The vent and filler pipe are a tiny amount down from the top of the tank. So like you say ... space for expansion.



This tank *is* going to fill to 102% capacity. The other 2% being the filler pipe. It'll click out when the sucker is FULL See the fittings are on the top of the tank. In normal filling it's going to fill to the top of the filler neck leaving no air space in the tank. The funny little separation tank is going to have act as an expansion tank too.

I learnt something today, I'd never realised before a correctly designed tanks doesn't fill right to the top. Now I think about it, all my cars petrol tanks always leave a small air gap at the top!

I just thought of another possibility.... I'll check the vent tube and filler tube tonight... possibly the filler and vent pipe on the top of that tank drops an inch down into the tank so an air space is left at the top. I can't imagine LRA would make such a mistake when they make tanks as a living. So I'm sure this will all work fine once I've fixed up the breathers.

seeya,
shane L.